Ultrasound sensors in which a semiconductor substrate having an opening portion, two layers of electrodes on an insulating film layer formed on the surface of the semiconductor substrate while blocking the opening portion and a PZT ceramic thin film layer interposed between the two layers of electrodes are arranged in an array form are known in the related art (for example, refer to JP-A-2010-164331).
In such an ultrasound sensor, a piezoelectric material forming the piezoelectric layer has to be replaced in order to control transmission sensitivity and reception sensitivity. That is, in a case where a dedicated transmission type element and a dedicated reception type element are provided, the elements having different piezoelectric materials have to be arranged, which is very difficult. In a case of unifying the piezoelectric materials, even though the transmission sensitivity and the reception sensitivity are able to be adjusted by varying, for example, a size of an opening portion, it is practically and actually difficult to use since a resonance frequency will be varied according to the varied size of the opening.
The invention was created in consideration of the above-described situation and an object thereof is to provide an ultrasound sensor in which the piezoelectric materials are the same and the elements having different transmission-reception sensitivity are provided together, without varying the resonance frequency.